Normalized backend models silently render as dashes in JS frontends

When a Python backend maps a provider payload into a pydantic model and returns model_dump(), the wire keys become the model field names (last, prev_close, close) while the frontend may still read the provider-native nested keys (snapshot.latestTrade.p, bar.c). This fails silently rather than throwing: Number(undefined || undefined || 0) is 0, and a guard like {last ? fmtMoney(last) : String.fromCharCode(8212)} then renders an em-dash, so the UI looks like a data-availability problem instead of a shape mismatch. If a pydantic model stores the provider payload in a raw dict field, grep the frontend for those raw nested key paths before assuming the integration works. Fix by defining one canonical wire shape and making the normalizer emit every key always present (null for no data) so unpriced rows cannot be distinguished from malformed ones.